<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot>

      </slot>
    </div>
    <!-- <div class="dots">
      <span class="dot" v-for="(item ,index) in dots" :class="{active:currentPageIndex===index}"></span>
    </div> -->
  </div>
</template>

<script type="text/ecmascript-6">
import BScroll from 'better-scroll'
import { addClass, getStyle } from '@/common/js/dom'

export default {
  data() {
    return {
      dots: [],
      currentPageIndex: 0
    }
  },
  props: {
    loop: {
      type: Boolean,
      default: false
    },
    autoplay: {
      type: Boolean,
      default: false
    },
    interval: {
      type: Number,
      default: 4000
    }
  },
  mounted() {
    setTimeout(() => {
      this._setSliderWidth()
      this._initDots()
      this._initSlider()
      if (this.autoplay) {
        this._play()
      }
    }, 20)
    window.addEventListener('resize', () => {
      if (!this.slider) {
        return
      }
      this._setSliderWidth(true)
      this.slider.refresh()
    })
  },
  methods: {
    _setSliderWidth(isResize) {
      this.children = this.$refs.sliderGroup.children
      let width = 0
      let sliderWidth = this.$refs.slider.clientWidth
      for (let i = 0; i < this.children.length; i++) {
        let child = this.children[i]
        addClass(child, 'slider-item')

        // child.style.width = sliderWidth + 'px'
        width += parseInt(getStyle(child, 'width'))
      }
      if (this.loop && !isResize) {
        width += 2 * sliderWidth
      }
      this.$refs.sliderGroup.style.width = width + 'px'
    },
    _initDots() {
      this.dots = new Array(this.children.length)
    },
    _initSlider() {
      this.slider = new BScroll(this.$refs.slider, {
        scrollX: true,
        scrollY: false,
        momentum: true, // 惯性滑动
        snap: false, // 整屏滚动
        snapLoop: this.loop,
        snapThreshold: 0.3,
        snapSpeed: 400,
        click: true
      })
      this.slider.on('scrollEnd', () => {
        let pageIndex = this.slider.getCurrentPage().pageX
        if (this.loop) {
          pageIndex -= 1
        }
        this.currentPageIndex = pageIndex
        if (this.autoplay) {
          clearTimeout(this.timer)
          this._play()
        }
      })
    },
    _play() {
      let pageIndex = this.currentPageIndex + 1
      if (this.loop) {
        pageIndex += 1
      }
      this.timer = setTimeout(() => {
        this.slider.goToPage(pageIndex, 0, 400)
      }, this.interval)
    }
  },
  destroyed() {
    clearTimeout(this.timer)
  }
}
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
@import '~@/common/stylus/variable'
// .slider
//   min-height 1px
//   position relative
//    overflow hidden
//   .slider-group
//     position relative
//     flex-flow: row nowrap
//     display flex
//     .slider-item
//       text-align center
//       flex 1
//       a
//         display block
//         width 100%
//         overflow hidden
//         text-decoration none
//       img
//         display block
//         // width 100%
//   .dots
//     position absolute
//     right 0
//     left 0
//     bottom 12px
//     text-align center
//     font-size 0px
//     .dot
//       display inline-block
//       margin 0 4px
//       width 8px
//       height 8px
//       -webkit-border-radius 50%
//       -moz-border-radius 50%
//       border-radius 50%
//       background $color-text-l
//       &.active
//         width 20px
//         -webkit-border-radius 5px
//         -moz-border-radius 5px
//         border-radius 5px
//         background $color-text-ll
</style>

